Lung fibrosis is a frequent consequence of chronic inflammatory processes and environmental exposures. Several cytokines contribute to fibrosis in the lungs and other organs. Previous reports from numerous laboratories indicate that targeting only one of these factors may ameliorate fibrosis in animal models, suggesting that development of fibrosis is a highly integrated process, and that targeting of a single cytokine may become an important therapeutic option. Targeting organ-specific profibrotic factors may lead to fewer side effects than targeting ubiquitous cytokines. Available data suggest that pulmonary and activation-regulated chemokine, PARC, a recently discovered lung-specific CC chemokine, may be an independent lung-specific key factor contributing to lung fibrosis through its dual action - 1) indirectly by attracting T cells and stimulating production of profibrotic cytokines from these T cells, and 2) directly by activating collagen production from lung fibroblasts. Understanding mechanisms of the direct profibrotic effect of PARC is the subject of this study. The specific hypothesis of this study is that PARC activates collagen production in human lung fibroblasts by binding to a specific cell surface receptor, signaling through the ERK pathway, activating transcription factor Sp1, activating transcription of collagen, and finally causing lung fibrosis. To test this hypothesis, the following Specific Objectives will be addressed: 1. Identify the PARC-specific receptor(s) on lung fibroblasts, determine whether other molecules are involved in PARC binding, and characterize the binding kinetics of PARC to its receptor(s). 2. Characterize activation of the ERK pathway and Sp1 in lung fibroblasts by PARC and establish whether PARC-dependent activation of Sp1 is mediated by the ERK pathway. Determine the role of ERK and SP1 activation in PARC-stimulated collagen production in lung fibroblasts. 3. Using deletion constructs of the collagen promoter, locate response elements involved in transcriptional regulation of collagen by PARC. Determine whether increased mRNA stability also contributes to PARC-stimulated upregulation of collagen production. 4. Analyze the effects of pulmonary adenovector-mediated gene transfer of PARC on lung fibrosis in intact mouse lung and bleomycin-treated mouse lung.